Methods and assemblies for gas flow ratio control

ABSTRACT

Methods and gas flow control assemblies configured to deliver gas to process chamber zones in desired flow ratios. In some embodiments, assemblies include one or more MFCs and a back pressure controller (BPC). Assemblies includes a controller, a process gas supply, a distribution manifold, a pressure sensor coupled to the distribution manifold and configured to sense back pressure of the distribution manifold, a process chamber, a one or more mass flow controllers connected between the distribution manifold and process chamber to control gas flow there between, and a back pressure controller provided in fluid parallel relationship to the one or more mass flow controllers, wherein precise flow ratio control is achieved. Alternate embodiments include an upstream pressure controller configured to control flow of carrier gas to control back pressure. Further methods and assemblies for controlling zonal gas flow ratios are described, as are other aspects.

FIELD

The present invention generally relates to gas flow control to processchambers for electronic device manufacturing, and more particularly tomethods and assemblies for gas flow ratio control.

BACKGROUND

Semiconductor processing wherein a substrate is processed in a processchamber can be particularly sensitive to process gas flow ratevariations and perturbations. In particular, variations may affect oneor more critical dimensions and/or film thicknesses during processing,for example. Thus, gas delivery assemblies for semiconductor processingchambers attempt to deliver steady flows at precise flow rates, flowratios, and pressures to multiple input ports of a process chamber.

Prior art gas delivery assemblies may utilize flow-splitting methods toimprove flow ratio accuracy, repeatability, and reproducibility inmulti-injection point and/or multi-chamber processing systems. Flowsplitting can be provided by using a plurality of mass flow controllers(MFCs), which actively attempt to control the relative flow rates ofgases dispensed at the multiple input port locations. However, as newchamber processing technologies continue to achieve smaller criticaldimensions for microelectronic devices, even higher degrees of flowcontrol precision, and in particular, flow ratio control, arebeneficial. Therefore, methods and assemblies are desirable for makinggas flow rate control, and in particular, flow ratio control, moreprecise.

SUMMARY

In one or more embodiments, a method of controlling flow of a gas to aprocess chamber is provided. The method includes providing adistribution manifold fluidly coupled to the a process chamber,providing one or more mass flow controllers fluidly coupled between theprocess chamber and the distribution manifold, providing a back pressurecontroller fluidly coupled to the distribution manifold, controllingflow through each of the one or more mass flow controllers to adynamically-controllable flow set point, and controlling back pressureupstream of the back pressure controller to a back pressure set point.

In some embodiments, a gas flow control assembly is provided. The gasflow control assembly includes a controller, a process gas supply, adistribution manifold fluidly coupled to the process gas supply, apressure sensor coupled to the distribution manifold and operativelyconnected to sense gas pressure in the distribution manifold, a processchamber, one or more mass flow controllers, each mass flow controllerfluidly and operatively connected to the distribution manifold and theprocess chamber to control gas flow there between, and a back pressurecontroller fluidly and operatively connected to the distributionmanifold.

In further embodiments, a gas flow control assembly is provided. The gasflow control assembly includes a controller, a process gas supply, adistribution manifold fluidly coupled to the process gas supply, thedistribution manifold having at least two outlets, a back pressuresensor operatively connected to the controller and configured to sensegas pressure in the distribution manifold, a process chamber, one ormore mass flow controllers, each of the one or more mass flowcontrollers fluidly and operatively connected to an outlet of thedistribution manifold and to a zone of the process chamber to controlgas flow percentage into each zone, a back pressure controller fluidlyconnected to the distribution manifold and operatively connected to thecontroller to control the back pressure controller to a back pressureset point responsive to output from the back pressure sensor.

In further embodiments, a method of controlling flow of a gas to aprocess chamber is provided. The method includes providing adistribution manifold fluidly coupled to a process chamber, providing aprocess gas supply fluidly coupled to the distribution manifold, theprocess gas supply including an upstream pressure controlleroperationally coupled to a carrier gas, and one or more process gaseswhose flow is controlled by one or more supply mass flow controllers,providing one or more mass flow controllers fluidly coupled between theprocess chamber and the distribution manifold; controlling gas flowthrough each of the one or more mass flow controllers to adynamically-controllable flow set point, and controlling back pressureof the distribution manifold to a back pressure set point by controllingcarrier gas flow with the upstream pressure controller.

According to one or more embodiments, a gas flow control assembly isprovided. The gas flow control assembly includes a controller, a processgas supply including a carrier gas and one or more process gases, adistribution manifold fluidly coupled to the process gas supply, a backpressure sensor fluidly connected to the distribution manifold andconfigured to sense back pressure in the distribution manifold, aprocess chamber including a plurality of zones, a plurality of mass flowcontrollers, each of the mass flow controllers fluidly and operativelyconnected between the distribution manifold and the process chamber andconfigured to control gas flow into the plurality of zones of theprocess chamber, and an upstream pressure controller fluidly andoperatively connected to the distribution manifold and configured tocontrol flow of the carrier gas responsive to a back pressure set pointsupplied by the controller.

In yet another embodiment, a gas flow control assembly is provided. Thegas flow control assembly includes a controller, a process gas supplyincluding a carrier gas and one or more process gases configured to bemixed at a junction, a distribution manifold fluidly coupled to theprocess gas supply downstream of the junction, the distribution manifoldhaving a plurality of outlets, a back pressure sensor operativelyconnected to the controller and configured to sense back pressure in thedistribution manifold, a process chamber including a plurality of zones,one or more mass flow controllers, each of the one or more mass flowcontrollers fluidly and operatively connected to an outlet of thedistribution manifold and to one of the plurality of zones to control agas flow ratio into each of the plurality of zone, and an upstreampressure controller fluidly connected to the carrier gas upstream of thejunction, and operatively connected to the controller to control theback pressure to a back pressure set point responsive to an outputsignal from the back pressure sensor.

Numerous other features are provided in accordance with these and otheraspects of the invention. Other features and aspects of embodiments ofthe present invention will become more fully apparent from the followingdescription, the appended claims, and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic top view of a gas flow control assemblyincluding a mass flow controller and a back pressure controlleraccording to one or more embodiments.

FIG. 2 illustrates a schematic top view of an alternative embodiment ofa gas flow control assembly including a mass flow controller and a backpressure controller wherein the back pressure controller output bypassesthe process chamber according to one or more embodiments.

FIG. 3 illustrates a schematic top view of another embodiment of a gasflow control assembly including multiple mass flow controllers and aback pressure controller according to one or more embodiments.

FIG. 4 illustrates a schematic top view of another alternate embodimentof a gas flow control assembly including multiple mass flow controllersand a back pressure controller wherein output from the back pressurecontroller bypasses the process chamber according to one or moreembodiments.

FIG. 5 illustrates a schematic top view of another embodiment of a gasflow control assembly including multiple mass flow controllers and apressure controller wherein output from a carrier gas supply is pressurecontrolled according to one or more embodiments.

FIG. 6 illustrates a schematic top view of an alternative embodiment ofa gas flow control assembly including multiple mass flow controllers anda pressure controller wherein output from a carrier gas supply ispressure controlled according to one or more embodiments.

FIG. 7 illustrates a schematic top view of an alternative embodiment ofa gas flow control assembly including multiple mass flow controllers anda pressure controller wherein output from a carrier gas supply ispressure controlled according to one or more embodiments.

FIG. 8 illustrates a flowchart of a method of controlling flow of a gasto a processing chamber including back pressure control according to oneor more embodiments.

FIG. 9 illustrates a flowchart of a method of controlling flow of a gasto a processing chamber including pressure control of output from acarrier gas supply according to one or more embodiments.

DESCRIPTION

The present invention provides improved methods and assemblies forcontrolling gas flow into a process chamber, such as semiconductorprocess chamber, or the like. In particular, embodiments of the presentinvention reduce flow variations, dithering, and/or flow starvation ofthe mass flow controllers (hereinafter MFCs) in the assembly as the MFCscompete for gas flow in order to meet desired flow set pointscontrolling flow ratios for each MFC.

Prior art methods of gas flow ratio control do not attempt to achievesteady state flow through MFCs coupled to the process chamber. Eachprior art MFC is set to its flow set point, which is generally apercentage of the total flow, and thus attempts to maintain constantflow at that set point percentage. However, any variation in theincoming flow causes back pressure variations and causes the variousMFCs to adjust their flow requirements. If the pressure is low, the onlyway to achieve more flow through a certain MFC is by starving another.Thus, transient flow through the MFCs is provided where all the MFCs inthe assembly constantly compete with one another to achieve theirrespective flow set points. As a result, undesirable flow variations mayoccur to each of the process chamber inlet ports. This may impactprocess quality and/or uniformity. This may cause non-uniform etch ordeposition, in some embodiments, for example. Embodiments of the presentinvention may substantially eliminate this competition between the MFCsand provided precise flow set point control and flow ratio control.

Further, embodiments of the present invention may allow the use of asimple feedback control method to control percentage set points to thedesired flow ratios.

One or more embodiments of the present invention provide a novelcombination of MFCs and a back pressure controller in a flow ratioapparatus in order to precisely control the respective flow ratios ofthe MFCs. Example embodiments of gas flow control assemblies and methodsincluding a back pressure controller for controlling flow of a gas to aprocessing chamber are described herein with reference to FIGS. 1-4 and8.

Example embodiments of gas flow control assemblies and methods includingan upstream pressure controller configured to control pressure of acarrier gas exiting from a process gas supply for controlling flow ofgas and gas flow ratios to a processing chamber are described withreference to FIGS. 4-7 and 9 herein.

Now referring to FIG. 1, a first example embodiment of a gas flowcontrol assembly 100 according to the present invention is depicted. Thegas flow control assembly 100 includes a controller 102 (e.g., a digitalcontroller with processor), a process gas supply 104, and a flow ratioapparatus 105 fluidly coupled to the process gas supply 104. The flowratio apparatus 105 may include a distribution manifold 106 fluidlycoupled to the process gas supply 104, which may provide a carrier gasand one or more process gases (e.g., process gases 1 through process gasN) to be used in the processing taking place in the process chamber 110.

The phrase “fluidly coupled” as used herein means that the componentsare coupled by conduits adapted to carry a fluid (e.g., gas) therethrough. The flow ratio apparatus 105 of the gas flow control assembly100 further includes a back pressure sensor 108 that may be fluidly andoperatively connected to the distribution manifold 106 and operativelyconnected to the controller 102 and configured to sense gas pressurewithin the distribution manifold 106 and provide to the controller anoutput signal thereof to be used for flow ratio control as will beapparent from the following.

The gas flow control assembly 100 further includes the process chamber110, which receives gas flow from the flow ratio apparatus 105. The flowratio apparatus 105 includes one or more mass flow controllers (MFCs)112 (one shown in the depicted embodiment), wherein each MFC 112 isfluidly and operatively connected to the distribution manifold 106 andto the process chamber 110 and operatively connected to the controller102 to control gas flow to one or more zones (e.g., Zone 1, Zone 2 A,Zone 2 B) of the process chamber 110. The process chamber 110 may be anychamber where a process takes place on a substrate 120 (shown dotted),such as an etch process chamber, a deposition process chamber (e.g.,atomic layer deposition (ALD), physical vapor deposition (PVD), orchemical vapor deposition (CVD) deposition), epitaxial deposition, acleaning process chamber, or the like.

The flow ratio apparatus 105 further includes a back pressure controller114 fluidly and operatively connected to the distribution manifold 106.In the depicted embodiment of FIG. 1, the back pressure controller 114may also be fluidly coupled to the processing chamber 110. In thedepicted embodiment, a single MFC 112 and a single back pressurecontroller 114 are provided in fluid parallel relationship. However,later embodiments will include a plurality of MFCs 112A, 112B inparallel with a single back pressure controller 114.

The MFC 112 is a device used to measure and control the flow of gases.The MFC 112 is designed and calibrated to control a specific or range oftypes of gas at a particular range of flow rates. The MFC 112 can begiven a dynamically-adjustable set point from 0% to 100% of its fullscale range, but is typically operated at about 10% to about 90% of fullscale range where the best accuracy may be achieved. The MFC 112 willthen control the rate of flow to an individual flow set point. MFCs canbe either analog or digital. A multi-gas and multi-range MFC isgenerally able to control more than one type of gas, and is thereforepreferred in cases where more than one gas recipe from the process gassupply 104 is supplied to the process chamber 110. A standard MFC may beused, but may be limited to a particular gas recipe for which it wascalibrated.

All MFCs 112 have an inlet port, an outlet port, an internal mass flowsensor, and a proportional control valve which is actuatable by anactuator (e.g., and suitable motor or automated motion causing element).The MFC 112 may be generally fitted with a closed loop control system,which may be given a flow set point control signal by the controller 102that is then compared to the value from the internal mass flow sensorand adjusts the proportional valve via actuation to achieve the desiredflow rate. The flow set point control signal may be generally specifiedas a percentage (a flow ratio) of its calibrated full scale flow and maybe supplied to the MFC 112 as a voltage from the controller 102. In someembodiments, the closed loop control system is provided as circuitrywithin the MFC 112, which is operatively connected to the controller 102and receives the flow set point control signal therefrom. In otherembodiments, the closed loop control may be accomplished solely bycontroller 102. All MFCs described herein are of this construction.

In the depicted embodiment, the MFC 112 is provided with a supply of gasat the inlet port thereof from the distribution manifold 106 and at adesignated back pressure that is set by the controller 102. Because theBPC 114 ensures that a desired back pressure is achieved in thedistribution manifold 106, the MFC 112 of the present embodiment cannotbe starved of gas and thus enables the flow set point and flow ratio tobe precisely achieved.

In the depicted embodiments, each of the MFCs 112 may be any suitablemodel of a mass flow controller having a normally closed valve, forexample, such as those available from HORIBA located in Kyoto, Japan.The MFCs 112 may be capable of handling flow rates of between about 10sccm and 200 slm, for example. For all embodiments described herein, theback pressure controller 114 may be any suitable pressure controller orpressure regulator for closed loop control of back pressure, such as aDigital Auto Pressure Regulator available from HORIBA located in Kyoto,Japan, or an integrated pressure controller for closed-loop pressurecontrol available from MKS of Andover, Mass. Back pressure controller114 includes an internal control valve that is actuatable via aninternal actuator and may include internal digital electronics toprovide a feedback control loop and actuation signal to control thebackpressure to a desired pressure set point communicated to the backpressure controller by controller 102. Backpressure sensor 108 may beinternally located in the back pressure controller 114 in someembodiments to sense backpressure in the distribution manifold 106.Closed loop control may optionally be carried out solely by thecontroller 102 or by any combination of the controller 102 and theinternal digital electronics.

As shown in FIG. 1, the process gas supply 104 is fluidly andoperatively connected to, and feeds process gas to, the distributionmanifold 106 of the flow ratio apparatus 105 through feed line 116. Feedline 116 may be a conduit or collection of conduits. The process gassupply 104 may include a plurality of different gases that may be mixed,as desired, for various processes that take place in the process chamber110. For example, in one embodiment, a carrier gas 118 may be provided,which is mixed with one or more process gases (Process Gas 1-N). Carriergas 118 may be any suitable gas for carrying process gases, such as anitrogen gas, hydrogen gas, an inert gas such as Helium, Argon, orcombinations thereof.

The process gas supply 104 may also include one or more process gases,such as the plurality of process gases (e.g., Process Gas 1 , ProcessGas 2, Process Gas 3, and up to Process Gas N). Process Gases 1-N may beused in carrying out one or more processes on a substrate 120 containedin the process chamber 110. The substrate 120 may be an electronicdevice precursor article, such as a semiconductor wafer, crystallinesilicon wafer, silicon wafer, doped silicon wafer, doped or un-dopedpolysilicon wafers, masked silicon wafer, patterned or un-patternedsilicon wafer, or a silicon-containing disc or plate, othersilicon-containing article, or the like. Substrate 120 may be stationedand supported for processing on a suitable support within the processchamber 110, such as a pedestal or lift pins, for example. The processchamber 110 may be a semiconductor processing chamber adapted to processa substrate 120 therein. The Process Gases 1-N may be a reductant gassuch as Oxygen (O₂), Carbon Dioxide (CO₂), Nitrogen Oxide (NO), NitrousOxide (N₂O), Nitrogen Dioxide (NO₂), Methane (CH₄), Carbon tetrafluoride(CF₄), Tetrafluoromethane (CHF₄), Trifluormethane (CHF₃),Difluoromethane (CH₂F₂), Chlorine Trifluoride (ClF₃), SulfurHexafluoride (SF₆), Hexafluorobutadiene (C₄F₆), Hexafluoroethane (C₂F₆),Octafluorocyclobutane (C₄F₈), Octafluorocyclopentene (C₂F₆),Octafluoropropane (C₃F₈), Propylene (C₃H₆), Nitrogen Trifluoride (NF₃),Dichlorsilane (H₂SiCl₂), Phosphine (PH₃), Silane (SiH₄), Trichlorsilane(TCS), Trimethylsilane (3MS), Boron Trichloride (BCl₃), Chlorine (Cl₂),Ammonia (NH₃), Germane (GeH₄), Tungsten Hexafluoride (WF₆), Xenon (Xe),or the like, for example. Other suitable process gases may be used.

In more detail, the process gas supply 104 may include a plurality ofsupply MFCs, such as supply MFC 124 ₁ through supply MFC 124 _(N),wherein N may be equal to the number of process gases that are presentthereat. For example, there may be three or more supply MFCs, such assupply MFCs 124 ₁, 124 ₂, 124 ₃ and 124 _(N). Other numbers of processgases and supply MFCs may be used. The process gas supply 104 mayfurther include control valves 125, 126 operatively connected to thecontroller 102 to control the relative flow and ratio of the carrier gas118 to process gases (Process Gas 1, Process Gas 2, Process Gas 3, . . ., Process Gas N) and thus control not only the ratio of carrier gas 118to process gas, but also the total gas flow provided to the distributionmanifold 106 of the flow ratio apparatus 105. The process gas flow setpoints for each of the supply MFC 124 ₁-124 _(N) as well as the flowthrough control valves 125, 126 are determined and set by controller 102according to the desired recipe for the particular process or stage ofthe process taking place at the process chamber 110 at that time.

The process gas supply 104 is operatively coupled to and provided influid communication with the flow ratio apparatus 105, which includesthe distribution manifold 106, one or more MFCs 112, back pressurecontroller 114, and the back pressure sensor 108. Depending on theprocess recipes to be supplied during semiconductor substrateprocessing, the number of different process gases supplied to the flowratio apparatus 105 from the supply MFCs 124 ₁-124 _(N) may vary.Moreover, the relative ratios of the total flow to various zones (e.g.,Zone 1, Zone 2A, and Zone 2B) of the process chamber 110 may also bevaried.

As such, the process chamber 110 may be adapted to receive gases in morethan one zone within the process chamber 110 and thus an output manifold130 may be provided that is coupled to the one or more MFC 112 and theBPC 114 and may include multiple manifold sections 130A-130C feedinginto the process chamber 110 at multiple zones. The flow ratio apparatus105 functions to allow flow of the gas through the one or more mass flowcontrollers 112 and the back pressure controller 114 and into one ormore zones (e.g., Zone 1, Zone 2A, zone 2B) of the process chamber 110.Different flows to two or more zones may be provided.

As depicted in FIG. 1, the flow ratio apparatus 105 may be coupled tothe output manifold 130 that may couple at their respective outputs ofoutput manifold sections 130A-130C to multiple zones (e.g., zone 1, zone2 A and Zone 2B) of the process chamber 110. For example, flow from theMFC 112 may be routed to an inner zone (e.g., zone 1) by output manifoldsection 130A and gas flow from the back pressure controller 114 may beprovided to one or more outer zones (e.g., zone 2A and zone 2B) byoutput manifold sections 130B, 130C. The output manifold sections 130A,130B, 130C may include multiple output channels that may be distributedwithin each respective zone, for example. In some embodiments, the zones(e.g., Zone 1, Zone 2A, and Zone 2B) may be arranged horizontally acrossthe process chamber 110, as shown. In other embodiments, multiple zonesmay be arranged as one or more concentric rings arranged around acircular center zone. Other zone arrangements may be used to providezonal gas flow control. In other embodiments, some outputs may bearranged at a top of the process chamber 110 while other may be arrangedon a side or even on a bottom of the process chamber 110 or anycombination thereof. Multiple output ports to each zone (e.g., Zone 1,Zone 2A, and Zone 2B) may be provided.

In the depicted embodiment, the MFC 112 is controlled to a flow setpoint by way of interaction and communication with the controller 102.The flow set point of the MFC 112 may be set such that a desired ratio(e.g., 60%) of the total flow provided in feed line 116 from gas supply104 is provided to Zone 1, for example. The remaining gas flow to theZone 2A and Zone 2B may then be set based upon a designed back pressurethat is desired in the distribution manifold 106. In particular, theback pressure controller 114 is configured and operable to control thebackpressure to a predetermined back pressure set point (Pb). Forexample, the designed back pressure set point (Pb) may be between about50 Torr and about 1600 Torr, and about 350 Torr in some embodiments, forexample. Other back pressure set points (Pb) may be used. In someembodiments, the back pressure set point (Pb) may be set based upon thepressure of the gas supply minus the pressure of the process chamber110.

In other embodiments, more than one MFC 112 may be used. For example, afirst MFC 112 coupled to the distribution manifold 106 may control afirst flow ratio to a first zone (e.g., Zone 1) and a second MFC (notshown) coupled to the distribution manifold 106 may control a secondflow ratio to a second zone (e.g., Zone 2A) whereas the BPC 114 maycontrol flow to the third zone (e.g., zone 2B) responsive to the desiredback pressure set point (Pb). Even more numbers of MFCs may be used toprovide even finer flow ratio control to additional zones of the processchamber 110. In this manner, the multiple MFCs do not fight with oneanother for flow, because the flow ratio through each MFC can becontrolled to very tight tolerances, such as even +/−1% or less.Likewise, a tight tolerance of about +/−1% or less can be provided forthe flow set point for each MFC 112.

Controller 102 herein may include a suitable processor, memory, andsoftware, firmware, or combinations thereof, A/D converters,conditioning electronics, and/or drivers to control the flow from theprocess gas supply 104, control the each MFC 112 to the desired flow setpoint and receive back pressure signals in order to control the backpressure in the distribution manifold 106 via control signals to theback pressure controller 114 of the desired back pressure set point(Pb). The desired back pressure set point (Pb) may be responsive to thepressure signals received by controller 102 by back pressure sensor 108.Flow set point may be set between about 0.5% and 99.5% of the total fullrange flow in the depicted embodiment, for example. In some embodiments,the flow set point should be between about 5% and about 95%. In someembodiments, the sensor 108 may be provided as an integral part of thewith BPC 114, and internal closed loop electronics of the BPC 114 maythen control the back pressure to the back pressure set point (Pb)supplied to the internal closed loop electronics by controller 102 thatis communicatively connected thereto. In other embodiments, closed loopcontrol may be accomplished by any suitable combination of the internalclosed loop electronics and the controller 102.

FIG. 2 depicts details of an alternate embodiment of a gas flow controlassembly 200. The gas flow control assembly 200 includes the controller102, process gas supply 104, and process chamber 110, identical aspreviously described. Other items not specifically described are thesame as in the FIG. 1 embodiment. In this embodiment, however, the flowratio apparatus 205 includes a first MFC₁ 112A that is operatively andfluidly coupled to a first zone (e.g., Zone 1—a center zone) of theprocess chamber 110, and a second MFC₂ 112B that is operatively andfluidly coupled to at least one other zone (e.g., to Zone 2A and Zone2B, as shown) of the process chamber 110. The BPC 114 in this embodimentof the flow ratio apparatus 205 controls the back pressure to a backpressure set point (Pb) by way of the controller 102 monitoring backpressure of the distribution manifold 206 via back pressure sensor 108and making suitable adjustments to an internal control valve in the BPC114.

As indicated above, the sensor 108 may be integral with BPC 114 in someembodiments, and closed loop control may be accomplished by internalclosed loop electronics of the BPC 114 to control the back pressure tothe back pressure set point (Pb) supplied to the internal closed loopelectronics by controller 102, or in some embodiments by processingcarried out by a combination of the internal closed loop electronics ofthe BPC 114 and the controller 102.

In the FIG. 2 embodiment, the outflow of the BPC 114, rather thanfeeding to the process chamber 110, bypasses the process chamber 110 andis fluidly coupled with, and flows to, a vent or scrubber 232. Theexhaust gas from the exhaust line 234 may be sent to vent, i.e., ventedto atmosphere if the gas is not in need of any treatment, oralternatively sent to an abatement system (e.g., a scrubber) should thegas be toxic or flammable and in need of treatment. Any suitableabatement system may be used for treatment, such as is described in USPub. Nos. US20100192773; 20100119984; 20090175771; and US20090056544;and in U.S. Pat. Nos. 8,668,868; 8,003,067; and 6,277,347, for example.Other suitable abatement systems may be used.

Each of the MFCs 112A, 112B may have flow set points to be set tobetween about 0.5% and 100% of the total gas flow. In one embodiment,the first MFC 112A may be set to a flow set point of about 85% of thetotal flow and the second MFC 112B may be set to a flow set point ofabout 10% of the total flow and the back pressure set point (Pb) may beset to about 800 Torr via operation of the BPC 114 so that less thanabout 5% of the total flow is exhausted in exhaust line 234. The totalflow may be set slightly higher to account for the gas loss to the ventor scrubber 232. Because there is a constant back pressure of the valueset by (Pb) provided in the distribution manifold 206, the first andsecond MFCs 112A, 112B can be precisely controlled and precisely held attheir selected flow set points, and thus precise flow ratio control tomultiple zones (e.g., Zone 1, Zone 2A, Zone 2B) of the process chamber110 may be achieved. Each of the mass flow controllers (e.g., MFC 112A,MFC 112B) may be configured and operatively connected to the process gassupply 104 in parallel so as to supply a high flow of gas from theprocess gas supply 104 at a flow rate of greater than about 90 slm,greater than 95 slm, or even greater than 100 slm in some embodiments.

FIGS. 3 and 4 represent additional embodiments of gas flow controlassemblies 300, 400 wherein the flow ratio apparatus 305 includesmultiple MFCs (e.g., MFC 1, MFC 2, MFC 3, MFC 4, . . . , MFCN). Asbefore, these embodiments include a process chamber 310, 410 configuredto contain and process substrates 120, and a distribution manifold 306.In this embodiment, a plurality of MFCs 112A-112N may be fluidly coupledbetween the process chamber 310, 410 and the distribution manifold 306.As before, a back pressure controller 114 is fluidly coupled to thedistribution manifold 306. However, in the FIG. 3 embodiment, flowthrough the BPC 114 is directed to the process chamber 310, whereas inthe FIG. 4 embodiment, flow through the BPC 114 bypasses the processchamber 410 entirely and is exhausted instead to a vent or scrubber 232.

The flow ratio apparatus 305 in each embodiment includes the pluralityof MFCs 112A-112N, the BPC 114, the distribution manifold 306, and theback pressure sensor 108. As before, the back pressure sensor 108 may beintegral with the BPC 114 in some embodiments. In each embodiment, thecontroller 102 is configured to control flow through each of the one ormore MFCs 112A-112N to a specific dynamically-controllable flow setpoint, i.e., that can be changed as the processing recipe changes. Theflow ratio set point for each MFC 112A-112N-1 may be set based upon userprescribed settings. Setting for MFCN 112N may be based upon the totalmass flow from the process gas supply less the percentage from each ofthe other MFC1 through MFCN-1. Likewise, in each embodiment, the backpressure of the distribution manifold 306 may be controlled bycontroller 102 to the back pressure set point (Pb) that has been set bythe user. The control may be responsive to feedback signals from theback pressure sensor 108, and thus, the BPC 114 receives the remainingbalance of the total flow. The back pressure set point (Pb) may be basedupon the pressure upstream at the process gas supply 304 minus apressure at the process chamber 310, 410 in some embodiments. In eachembodiment, a total mass flow provided in the feed line 316 to thedistribution manifold 306 is the sum of the set mass flows from eachMFC1 -MFCN of carrier gas and process gases 1-N responsive to signalsfrom controller 102. The process gas supply 304 may provide the desiredmix of carrier gas 118 and process gases (e.g., Process Gas 1, ProcessGas 2, Process Gas 3, . . . , Process Gas N) via control of supply MFCs126 ₁-126 _(N).

As should be recognized, in each of the foregoing embodiments,adjustments to the percentage of flow ratio to each input port of theprocess chamber 110, 310, 410 may be adjusted dynamically. The transienttime, i.e., settling time for the gas flow control assembly 100, 200,300, 400 to reach a steady state condition is relatively shortened whenthe respective flow ratios are changed, as the MFCs 112, and 112A-112Nare no longer competing for flow with one another when the BPC 114 isprovided in fluid parallel therewith.

Thus, it should be apparent that in the FIG. 3 embodiment, the pluralityof mass flow controllers 112A-112N supply the gas from the process gassupply 104 to the plurality of zones (e.g., zone Z1-Z4) of the processchamber 310, and the back pressure controller 114 supplies the gas toanother zone (e.g., Z 5) of the process chamber 410.

In the FIG. 4 embodiment, flow through MFC1-N 112A-112N are provided tomultiple zones (e.g., zones Z1-Z4) and the remaining flow is provided tothe back pressure controller 114 which bypasses the process chamber 410entirely and is exhausted directly to a one of a vent or a scrubber 232.The back pressure set point (Pb) of the back pressure controller 114 maybe set as described above.

FIG. 5 illustrates another embodiment of gas flow control assembly 500including a process gas supply 504 and a flow ratio controller 505,wherein the flow ratio controller 505 is similar to the FIG. 2embodiment, except that the BPC 114 has been replaced with an upstreampressure controller 514. The upstream pressure controller 514 may beused to control the pressure of the carrier gas 118 supplied into thefeed line 116 and thus may be used to remotely control the pressureprovided in the manifold 506. Upstream pressure controller may include avalve and internal electronics, and possibly an internal pressuresensor. As before, the back pressure sensor 108 may be integral with theupstream pressure controller 514 in some embodiments and the controller102 provides the pressure set point. In the depicted embodiment, theupstream pressure controller 514 may be located upstream of a junction536 where the carrier gas 118 and the one or more Process Gases 1-N mixtogether. The distribution manifold 506 is fluidly coupled to theprocess gas supply 504 downstream of the junction 536. In thisembodiment, the flow ratio controller 505 includes only two or more massflow controllers (e.g., MFC₁, MFC₂) controlling flow, but is devoid of aback pressure controller. Thus, in this embodiment, no gas is wasted as100% of the gas flowing from the process gas supply 504 is provided tothe process chamber 110. This also reduces abatement requirements. Gasflow may be provided to at least as many or more zones (e.g., Zone 1,Zone 2A, Zone 2B) of the process chamber 110 as the number of MFCs(e.g., MFC1, MFC2).

FIG. 6 illustrates another alternative embodiment of gas flow controlassembly 600 including a flow ratio controller 605, wherein the flowratio controller 605 is similar to the FIG. 3 embodiment, except thatthe BPC 114 has been replaced with an upstream pressure controller 614.The upstream pressure controller 614 may be used to control the pressureof the carrier gas 118 supplied into the feed line 316 and thus may beused to remotely control the pressure provided in the manifold 606. Asbefore, the back pressure sensor 108 may be integral with the upstreampressure controller 614 in some embodiments. As in FIG. 5, the upstreampressure controller 614 may be located upstream of a junction 536 wherethe carrier gas 118 and the one or more Process Gases 1-N mix together.In this embodiment, the flow ratio controller 605 includes only aplurality of mass flow controllers (e.g., MFC1, MFC2, MFC3, . . . ,MFCN) controlling flow into the process chamber 610, but is devoid of aback pressure controller 114. Thus, in this embodiment, no gas is wastedas 100% of the gas is provided to the process chamber 410 therebyreducing abatement requirements. Gas flow may be provided to at least asmany or more zones (e.g., Zone Z1-Z4) of the process chamber 410 asthere are numbers of MFCs.

FIG. 7 illustrates another alternative embodiment of gas flow controlassembly 700 including a process gas supply 704 and a flow ratiocontroller 605, wherein the flow ratio controller 605 is identical tothat described in the FIG. 6 embodiment. In this embodiment, an upstreampressure controller 714 may be used to control the pressure of thecarrier gas 118 supplied into the feed line 316 and thus may be used toremotely control the pressure provided in the manifold 606. As before,the back pressure sensor 108 may be integral with the upstream pressurecontroller 714 in some embodiments. As in FIGS. 5 and 6, the upstreampressure controller 714 may be located upstream of a junction 536 wherethe carrier gas 118 and the one or more Process Gases 1-N are mixedtogether. In this embodiment, the pressure controller 714 may beprovided in a fluid parallel relationship with a carrier gas MFCC 726.Thus, in this embodiment also, no gas is wasted as 100% of the gas isprovided to the process chamber 410 thereby reducing abatementrequirements. Only a part of the carrier gas flows through the upstreampressure controller 714. Thus, the carrier gas MFCC 726 can be set to adesired flow set point, and the upstream pressure controller 714 may bemodulated to control the back pressure of the distribution manifold 606to the desired back pressure set point (Pb). It should be understoodthat the arrangement of pressure controller 714 provided in a fluidparallel relationship with a carrier gas MFCC 726 may be applied to thestructure shown in FIG. 5, thereby replacing pressure controller 514,with all else remaining the same.

FIG. 8 illustrates a flowchart depicting an example method ofcontrolling flow of a gas to a process chamber (e.g., process chamber110, 310, 410) according to one or more embodiments of the presentinvention. The method 800 includes, in 802, providing a process chamber(e.g., process chamber 110, 310, 410) and a distribution manifold (e.g.,distribution manifold 106, 206, or 306), providing one or more mass flowcontrollers (e.g., MFCs 112, 112A and 112B, or 112A-112N) fluidlycoupled between the process chamber (e.g., process chamber 110, 310,410) and the distribution manifold (e.g., distribution manifold 106,206, 306) in 804, and providing a back pressure controller (e.g., backpressure controller 114) fluidly coupled to the distribution manifold(e.g., distribution manifold 106, 306) in 806.

The method 800 further includes, in 808, controlling flow through eachof the one or more mass flow controllers (e.g., MFCs 112, 112A and 112B,or 112A-112N) to a dynamically-controllable flow ratio set point, and,in 810, controlling back pressure upstream of the back pressurecontroller (e.g., back pressure controller 114) to a back pressure setpoint (Pb).

Note that although the above example method 800 is described as asequence of discrete steps, embodiments of the invention are not solimited. The steps described are merely for illustrative purposes tofacilitate understanding of one or more embodiments of the invention.Any number of additional or intermediate steps may be included, severalsteps may be omitted or combined, and any parts of any of the steps maybe broken into sub-steps. In addition, the particular sequence in whichthe steps are presented is merely to facilitate understanding of theinvention and it should be understood that these steps, or anycombination or sub-steps, may be performed in any suitable order,including simultaneously.

The dynamically-controllable flow set point in 808 for each of the oneor more mass flow controllers (e.g., MFCs 112, 112A and 112B, or112A-112N) may be set to any percentage of the total flow rate withinthe allowable range. In some embodiment, the nominal flow rate for theone or more mass flow controllers (e.g., MFCs 112, 112A and 112B, or112A-112N) may be controlled to +/−1%, and thus very accurate control offlow ratio between the respective MFCs is possible. Accordingly, itshould be recognized that precise flow splitting for 2 or more channelsmay be accomplished. Further, because the MFCs are no longer fightingwith one another, flow imbalances may be reduced, and settling times ofless than about 1 second for changes in respective flow ratios of themass flow controllers (e.g., MFCs 112, 112A and 112B, or 112A-112N) maybe achieved. Further, simple control algorithms may be used forimplementing the back pressure control, such as simple error feedbackcontrol, proportional control, and the like. Obviously moresophisticated feed forward controls or predictive controls may be used,but adequate response time may be achieved even using simple feedbackcontrol methods.

FIG. 9 illustrates a flowchart depicting another example method ofcontrolling flow of a gas to a process chamber (e.g., process chamber110, 410) according to one or more embodiments of the present invention.The method 900 includes, in 902, providing a distribution manifold(e.g., distribution manifold 506, 606) fluidly coupled to a processchamber (e.g., process chamber 110, 410). The method 900 furtherincludes, in 904, providing a process gas supply (e.g., process gassupply 504, 604, 704) fluidly coupled to the distribution manifold, theprocess gas supply including an upstream pressure controller (e.g.,upstream pressure controller 514, 614, 714) operationally coupled to acarrier gas (e.g., carrier gas 118), and one or more process gases(e.g., Process Gas 1, Process Gas 2, Process Gas 3, . . . , Process GasN) whose flow is controlled by one or more supply mass flow controllers(e.g., supply mass flow controllers 124 ₁, 124 ₂, 124 ₃, . . . , 124_(N)).

The method 900 further includes, in 906, providing one or more mass flowcontrollers (e.g., MFC1 112A and MFC2 112B, or MFC1 112A through MFCN112N) fluidly coupled between the process chamber and the distributionmanifold.

Operationally, the method 900 includes, in 908, controlling gas flowthrough each of the one or more mass flow controllers (e.g., MFC1 112Aand MFC2 112B, or MFC1 112A through MFCN 112N) to adynamically-controllable flow set point, and, in 910, controlling backpressure of the distribution manifold to a back pressure set point(e.g., back pressure set point Pb) by controlling carrier gas flow withthe upstream pressure controller (e.g., upstream pressure controller514, 614, 714).

Although certain carrier gases and process gases and certain pressureranges and flow rates are described herein, it should be understood thatembodiments of the present invention are equally useable with othergases, pressure ranges, and gas flow rates.

Accordingly, while the present invention has been disclosed inconnection with example embodiments thereof, it should be understoodthat other embodiments may fall within the scope of the invention, asdefined by the following claims.

The invention claimed is:
 1. A gas flow control assembly, comprising: afirst controller; a process gas supply including a carrier gas and oneor more process gases, wherein the process gas supply further includesone or more first mass flow controllers, and wherein each first massflow controller of the one or more first mass flow controllers iscoupled to the first controller; a distribution manifold fluidly coupledto the process gas supply; a back pressure sensor connected to the firstcontroller and fluidly connected to the distribution manifold, andconfigured to sense back pressure in the distribution manifold, andfurther configured to provide a signal to the first controller based, atleast in part, on sensed back pressure; a process chamber including aplurality of zones; a plurality of second mass flow controllers, eachsecond mass flow controller of the plurality of second mass flowcontrollers fluidly and operatively connected between the distributionmanifold and the process chamber, and configured to control gas flowinto the plurality of zones of the process chamber; and an upstreampressure controller fluidly and operatively connected to thedistribution manifold and configured to control flow of the carrier gasresponsive to a back pressure set point supplied by the firstcontroller.
 2. The gas flow control assembly of claim 1, wherein thefirst controller is configured to set a flow set point through each ofthe plurality of second mass flow controllers, and wherein the firstcontroller is a digital controller including a processor.
 3. The gasflow control assembly of claim 1, wherein each of the plurality ofsecond mass flow controllers is configured to flow a gas from theprocess gas supply at a flow rate of greater than 90 slm.
 4. The gasflow control assembly of claim 1, wherein the upstream pressurecontroller is configured to control a flow of the carrier gas to bemixed with the one or more process gases responsive to the back pressureset point supplied by the first controller.
 5. A gas flow controlassembly, comprising: a first controller; a process gas supply includinga carrier gas and one or more process gases; a distribution manifoldfluidly coupled to the process gas supply; a back pressure sensorconnected to the first controller and fluidly connected to thedistribution manifold, and configured to sense back pressure in thedistribution manifold, and further configured to provide a signal to thefirst controller based, at least in part, on sensed back pressure; aprocess chamber including a plurality of zones; a plurality of mass flowcontrollers, each mass flow controller of the plurality of mass flowcontrollers fluidly and operatively connected between the distributionmanifold and the process chamber, and configured to control gas flowinto the plurality of zones of the process chamber; an upstream pressurecontroller fluidly and operatively connected to the distributionmanifold and configured to control flow of the carrier gas responsive toa back pressure set point supplied by the first controller; and acarrier gas mass flow controller provided in a fluid parallelrelationship with the upstream pressure controller.
 6. A gas flowcontrol assembly, comprising: a first controller; a process gas supplyincluding a carrier gas and one or more process gases configured to bemixed at a junction, wherein the process gas supply further includes oneor more first mass flow controllers, and wherein each first mass flowcontroller of the one or more first mass flow controllers is coupled tothe first controller; a distribution manifold fluidly coupled to theprocess gas supply downstream of the junction, the distribution manifoldhaving a plurality of outlets; a back pressure sensor operativelyconnected to the first controller and configured to sense back pressurein the distribution manifold; a process chamber including a plurality ofzones; one or more second mass flow controllers, each of the one or moresecond mass flow controllers fluidly and operatively connected to anoutlet of the distribution manifold and to one of the plurality of zonesto control a gas flow ratio into each of the plurality of zones; and anupstream pressure controller fluidly connected to the carrier gasupstream of the junction, and operatively connected to the firstcontroller, wherein the upstream pressure controller is configured tocontrol the back pressure to a back pressure set point responsive to anoutput signal from the first controller that is responsive to an outputsignal from the back pressure sensor.